1. Field of the Invention
The present invention relates to a processing apparatus for performing processing on an object, such as, forming a film thereon, in the manufacturing process of a semiconductor device and, in particular, to a vacuum processing apparatus.
2. Description of the Related Art
In the process of manufacturing a semiconductor wafer, a one-by-one type CVD apparatus is used as a thin-film forming apparatus for forming an insulating film and silicon thin film on the surface of a semiconductor wafer. Such one-by-one type CVD apparatus has a hermetically sealed processing chamber for forming a film in a vacuum atmosphere and a mount table arranged within the processing chamber to hold the wafer in place. An electrostatic chuck is provided at the upper surface of the mount table to attract the semiconductor wafer in place through the utilization of an electrostatic force.
The electrostatic chuck is of such a type as to have a sandwich structure with a thin electroconductor covered at its upper and lower surfaces with an insulating layer. The electrostatic chuck holds the wafer in place under a coulomb force or Johnsen-Rahbeck force generated upon the application of a DC voltage to the electroconductor.
Further, the CVD apparatus calls for the in-plane uniformity, that is, an evenness of a temperature distribution in a plane of a to-be-processed object, from the standpoint of securing the uniformity of a film formed. To this end, a heating device has been provided for heating the to-be-processed object to a suitable temperature in the processing chamber. As such heating device use has been made a one which is provided on the lower surface side of the mount table in a position spaced from the electrostatic chuck and is adapted to transmit heat which is generated from a heating element of the heating device to that overlying electrostatic chuck by heat-conduction.
It has been required that electric power be fed from a high-voltage power source to the electrostatic chuck. To the heating element for heating the to-be-processed object it has been necessary to feed a large electric power, that is, a high electric current coming from a high-voltage power source. As the processing is done under a vacuum atmosphere as set out above, a discharge is liable to occur across the electro-conductors in the CVD film forming apparatus.
In the case where an electric power is fed to the electrostatic chuck or the heating device from that electric power source provided outside the processing chamber, a receptacle terminal for instance is provided at the mount table and, by forcing a plug terminal which is electrically connected to the power source into the receptacle, the plug terminal is set in electrical contact with contacts provided on the inside of the receptacle terminal.
For this reason, a discharge is liable to occur between a contacting area of the receptacle terminal's contact and plug terminal, on one hand, and other conductors in the processing chamber on the other.
Therefore, there may be the cases where various kinds of source gases intrude into a circumferential atmosphere around the contacting area of the receptacle terminal and remains there. As a result, various reaction products are deposited on the inner wall of the receptacle terminal near the contacting area and on the circumference of the plug terminal. Depending upon the kinds of source gases an electroconductive reaction product such as polysilicon is produced. A leak current is produced, through such an electroconductive reaction product, between the contacting area and the conductors in the processing chamber and there is a possibility that the electrostatic chuck and heating device will fail to operate due to no adequate power supply to them. Further, there is also possibility that the receptacle terminal and plug terminal will corrode due to the reaction product and that the inside of the processing chamber will be contaminated due to the separation of the reaction product.